getresuid, getresgid - get real, effective, and saved user/group IDs

getresuid() returns the real UID, the effective UID, and the saved set-user-ID of the calling process, in
       the  arguments  ruid,  euid,  and  suid,  respectively.   getresgid() performs the analogous task for the
       process's group IDs.

EFAULT One of the arguments specified an address outside the calling program's address space.

       Linux 2.1.44, glibc 2.3.2.

       The original Linux getresuid() and getresgid() system calls supported only 16-bit  user  and  group  IDs.
       Subsequently,  Linux  2.4  added  getresuid32()  and  getresgid32(),  supporting  32-bit  IDs.  The glibc
       getresuid() and getresgid() wrapper functions  transparently  deal  with  the  variations  across  kernel
       versions.

       Standard C library (libc, -lc)

       getresuid, getresgid - get real, effective, and saved user/group IDs

       On success, zero is returned.  On error, -1 is returned, and errno is set to indicate the error.

getuid(2), setresuid(2), setreuid(2), setuid(2), credentials(7)

Linux man-pages 6.9.1                              2024-05-02                                       getresuid(2)

       None.  These calls also appear on HP-UX and some of the BSDs.

#define_GNU_SOURCE         /* See feature_test_macros(7) */
       #include<unistd.h>intgetresuid(uid_t*ruid,uid_t*euid,uid_t*suid);intgetresgid(gid_t*rgid,gid_t*egid,gid_t*sgid);